I installed a new starter, but it is still making a grinding noise like before. I think I might need a new fly wheel.
Throughout my experiences working on them, I have come to learn that grinding sounds coming from Ford trucks are actually not that uncommon. There can be a few different solutions to eliminate these noises depending on what part is doing the grinding. Since you mentioned that there was a new starter installed in your car, it is unlikely that it is the cause of the grinding noise you are hearing.
Since you mentioned that you changed your starter and the flywheel may be suspect, next you may want to go ahead and climb back under the truck and remove the access panel under the bell housing of the transmission. This will give you access to the flywheel. Using a flashlight you can inspect the teeth on the flywheel for any abnormal wear, then use a ½ inch ratchet and correct size socket for the crankshaft pulley bolt, and turn the engine clockwise. This will allow you to slowly inspect the hidden areas of the flywheel that could be damaged. Be sure to mark the flywheel with white out or a marker so you can verify when you start and end as you rotate. If at any time you feel uncomfortable doing this, please enlist the assistance of a certified mobile mechanic. A damaged flywheel will need to be replaced.
If you are unable to see any issues with the flywheel itself, then the problem may lay in the electrical components of the vehicle. I have also seen scenarios where an additional ground strap needs to be installed to the engine block to ensure a more stable connection of the starter to engage. There are also other cases where the ignition switch has failed to supply proper voltage to the starting circuit causing the starter solenoid to partially engage which can create a grinding noise. As you can see, there are many reasons why you may be hearing a grinding noise coming from your truck, despite a starter change. In situations like this it is always best to enlist the assistance of a certified mechanic to inspect your vehicleand get you back on the road quickly and safely.